#45178 [Csd]: garbage collector and cyclic references

From: Date: Fri, 25 Jul 2008 07:44:31 +0000
Subject: #45178 [Csd]: garbage collector and cyclic references
References: 1  Groups: php.bugs 
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 ID:               45178
 User updated by:  thomas dot jarosch at intra2net dot com
 Reported By:      thomas dot jarosch at intra2net dot com
 Status:           Closed
 Bug Type:         Reproducible crash
 Operating System: Linux
 PHP Version:      5.3CVS-2008-06-04 (snap)
 Assigned To:      dmitry
 New Comment:

Thanks, Dmitry! Your fix works fine for both bugs.


Previous Comments:
------------------------------------------------------------------------

[2008-07-24 13:38:22] dmitry@php.net

This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.



------------------------------------------------------------------------

[2008-07-16 13:20:31] thomas dot jarosch at intra2net dot com

Thanks for looking into this, Dmitry!

So there are actually two problems, one memory corruption reported 
here and one memory leak report in #33595 or are they both memory 
corruptions?

------------------------------------------------------------------------

[2008-07-15 11:42:00] dmitry@php.net

The simplest case for this memory corruption.

<?php
class Foo {
    function Foo() {
    	$this->error = array($this,$this);
    }
}
$a =& new Foo();


------------------------------------------------------------------------

[2008-07-15 07:37:50] dmitry@php.net

At first, you have a serious issue in your code. "static" variables
MUST NOT be asigned by reference, because they are already references.
As result the singleton pattern just doesn't work. BTW the bug is really
exists. The simplified test case follows(changing "=& new" into "= new"
fixes memory corruption).

<?php
class Horde_History {
    function raiseError() {
        return debug_backtrace();
    }

    function Horde_History() {
        $this->error = $this->raiseError();
        echo "Memory usage: " . memory_get_usage() . "\n";
    }
}

for ($i=0;$i<100000;$i++) {
	$a =& new Horde_History();
}
?>

------------------------------------------------------------------------

[2008-06-05 09:13:20] thomas dot jarosch at intra2net dot com

Actually, the reproduce code from #33595 also leaks memory.

The statement about Horde is not 100% correct as only some singleton 
functions are affected. I mixed it up with another reference problem 
I fixed a while ago. Nontheless memory is leaked :-)

------------------------------------------------------------------------

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    http://bugs.php.net/45178

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